The purpose of this test is to measure the profile of a line on the face of monochrome cathode ray tube (CRT) in order to estimate the resolution capacity of the CRT. Since the display on a CRT often consists of a series of lines or line segments forming alphanumeric characters or graphics patterns the line width is an important parameter in the determination of the resolution. For this reason, the test method discussed below measures the horizontal and vertical (and possibly diagonal) profiles of the lines produced by the electron beam or beams. From these profiles, the line widths can be determined. Such a test for determining the size of the CRT spot is the first step in any resolution calculation. Note that line profiles can also be determined from measurements of the intensity contours of the CRT spot. This method of determining the line profile is not discussed in this document.

The line profile of the CRT spot is dependent on a number of factors in addition to the focused electron beam distribution at the screen. Some of these factors are:

1. Electron scattering in the screen and support structure

2. Light scattering due to the granular nature of the phosphor and the aluminum backing of the screen

3. Saturation of the phosphor

4. Internal reflections and absorption of light in the faceplate and panels mounted onto the faceplate

5. Optical coatings, etches, etc., on the faceplate or panel

External influences on the resolution of the CRT, including ambient light, are not discussed in this method. These include the transfer characteristics of the viewing system, in particular, the non-linear response of a human observer.

Determination of the resolution of a CRT is a complex problem which is not completely solved at the present time. The reader is urged to consult the current literature before making any conclusions about the resolution of the display.